1. Field of Invention
The invention relates generally to brake control systems of a vehicle and methods for controlling brake systems, and more specifically to brake control systems of a vehicle and methods for controlling braking by selectively increasing and decreasing braking power of a wheel.
2. Description of Related Art
As an example of a brake control system of a vehicle such as an automobile, a brake control system such as that disclosed in Japanese Patent Application Laid-Open Publication No. 4-63755, which is constructed so as to perform anti-skid control by controlling so as to selectively increase and decrease wheel cylinder pressure with a differential pressure control valve, for example, has been known.
According to the above brake control system, the wheel cylinder pressure is able to be controlled to selectively increase and decrease linearly by controlling a control current to the differential pressure control valve. Therefore, abnormal noise generated during brake control, as well as kickback, are able to be reduced compared to when a switching valve, which is a valve to control an increase/decrease in pressure, is controlled so as to continuously switch.
According to the aforementioned brake control system, however, the wheel cylinder pressure is only selectively increased and decreased by the differential pressure control valve without the actual wheel cylinder pressure being detected. As a result, the wheel cylinder pressure is not able to be properly controlled with good accuracy to a target pressure. There is therefore room for improvement on this point in order to improve brake control performance, such as anti-skid control, of a vehicle.
Moreover, an electronic brake control system having an electronic pressure exerting device such as an electric motor for pressing a friction member such as a brake pad against a rotating member such as a brake rotor provided in a wheel has also been known. In this type of electronic brake control system as well, in order to accurately control the brake force, the target pressing force of the pressure exerting device must be properly set based on the state of the vehicle and the pressure exerting device must be controlled so that the difference between the target pressing force and the pressing force of the friction member against the rotating member detected by a pressing force sensor is reduced.